1. Field of the Invention
The present invention relates to a photoresist composition and a method of forming a pattern using the same, and more particularly to a photoresist composition having good sensitivity and residual layer characteristics.
2. Description of the Related Arts
Flat panel display devices have become increasingly popular because they are thin, light, and have low power consumption characteristics.
Among the flat panel devices, liquid crystal display (LCD) devices have been widely utilized because in addition to the above advantages, LCD devices are capable of displaying a high quality image. LCD devices are widely used as computer monitors and more recently as television units.
As LCD devices become larger, manufacturing becomes more complex. One reason is because the need for an enlarged glass, and the need to use a photoresist composition satisfying new process conditions, such as, processes for fabricating the fine featured patterns of circuits.
In general, photoresist composition characteristics such as photoresist layer sensitivity, developing contrasts, photoresist layer resolution, adhesiveness of underlying layers including substrates, and residual layer characteristics of the photoresist layer directly or indirectly influence the quality of the devices.
A conventional method of forming photoresist patterns is performed by using a common photolithography and photoresist composition. The method involves first forming a photoresist layer by applying a photoresist composition on a substrate. A mask having a predetermined pattern to selectively expose a predetermined portion of the photoresist layer is positioned above the photoresist layer and the photoresist layer is exposed to light through the mask. Then, a portion having a high solubility (the exposed portion for a positive photoresist) is typically removed by using a developing solution (typically referred to as development process) and a portion having a low solubility remains, to thereby obtain a photoresist pattern. Then, the exposed portions are etched to form a pattern on the substrate, and the remaining photoresist is removed to obtain a desired pattern such as a wire or an electrode.
U.S. Pat. Nos. 3,046,118, 3,106,465, 3,148,983, 4,115,128, and 4,173,470 and Japanese Patent Laid-open Publication No. Sho 62-28457 disclose a photoresist polymer having a novolak resin of cresol-formaldehyde and a naphthoquinone diazide-substituted photosensitive material. U.S. Pat. No. 5,648,194 discloses a photoresist composition containing alkali-soluble resins, o-naphthoquinone diazide sulfonic acid ester, and vinyl ether. U.S. Pat. No. 5,468,590 discloses a photoresist compositions containing alkali-soluble resins prepared by using quinone diazide compounds and polyphenol. U.S. Pat. No. 5,413,895 discloses a photoresist polymer having novolak resins, quinone diazide compounds, and polyphenol.
Generally, the photoresist polymer should have characteristics of: high sensitivity to light and good residual layer characteristic, despite their complementary relationship. Sensitivity means a changing rate of the solubility of a photoresist layer into a developing solution after exposure to light. The residual layer characteristic means a ratio of a thickness of a residual layer after developing with respect to an original thickness of the photoresist layer. Typically, as sensitivity increases, the residual layer characteristic is deteriorated. Accordingly, it would be highly desirable to develop photoresist compositions having both high sensitivity and good residual layer characteristic.